perf/x86: Micro-optimize nhmex_rbox_get_constraint()

Flipping the LSB doesn't require four lines of code. This shaves a few
bytes of the generated code, including a branch.

Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1403183731-15402-1-git-send-email-linux@rasmusvillemoes.dk
Signed-off-by: Ingo Molnar <mingo@kernel.org>

diff --git a/arch/x86/kernel/cpu/perf_event_intel_uncore.c b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
index 65bbbea38b9c9c0f7246a3c4fee4176dd529647b..e009f3cedf89ba8c31cf369e2501b917559588fd 100644 (file)
--- a/arch/x86/kernel/cpu/perf_event_intel_uncore.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_uncore.c
@@ -2946,10 +2946,7 @@ again:
                 * extra registers. If we failed to take an extra
                 * register, try the alternative.
                 */
-               if (idx % 2)
-                       idx--;
-               else
-                       idx++;
+               idx ^= 1;
                if (idx != reg1->idx % 6) {
                        if (idx == 2)
                                config1 >>= 8;